1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, a method of manufacturing the LCD device and an alignment layer composition used for the LCD device. More particularly, the present invention relates to an LCD device capable of enhancing display quality by improving the viewing angle and the response time, a method of manufacturing the LCD device and an alignment layer composition used for the LCD device.
2. Description of the Related Art
Generally, in a liquid crystal display (LCD) device, a voltage is applied to an electric field generating electrode to provide the liquid crystal layer with an electric field. The arrangement of liquid crystal molecules of the liquid crystal layer is controlled in response to the electric field, thereby displaying images.
In order to obtain a high contrast ratio and a wide viewing angle, a patterned vertical alignment (PVA) mode LCD device has been developed. In the PVA mode LCD device, an opening portion (hereinafter, a slit portion) having a slit shape is formed through the electric field generating electrode, and liquid crystal molecules are vertically aligned to form multiple domains.
For a small to medium-size mobile LCD device, in order to decrease the slit portion which decreases an aperture ratio, a microslit mode LCD device or a super patterned vertical alignment (S-PVA) mode LCD device has been developed. In the microslit mode LCD device, the microslit portion is only formed through a lower electrode of the electric field generating electrodes to provide directionality to the liquid crystal molecules. The upper electrode is formed from a continuous layer in which an opening portion is not formed.
In a vertical alignment (VA) mode such as the PVA mode and the microslit mode, a rubbing process is not performed directly on an alignment layer; however, a light alignment method, which includes aligning liquid crystal molecules by inducing anisotropy in an alignment layer through light irradiation, may be employed.
To align the liquid crystal molecules, a photocrosslinkable copolymer including a mesogenic group, called a reactive mesogen (RM), having liquid crystal properties, is irradiated by polarized ultraviolet (UV) light to induce anisotropy, and heat processing is performed on the photocrosslinkable copolymer to enhance the anisotropy of the alignment layer.
However, the RM may not be easily cured at a surface of the alignment layer, and the RM may remain in the liquid crystal layer. The RM remaining in the liquid crystal layer may be cured by light from a backlight of the LCD device. Cured amounts of the RM are different from each other depending on their location so that the pretilt angles of the liquid crystal molecules may not be uniform. As a result, afterimages may be seen on a display screen.
Using high-intensity UV light to completely remove an RM from the liquid crystal molecules may cause organic material decomposition and reliability deterioration.